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1.
D. M. Pechersky A. A. Lyubushin Z. V. Sharonova 《Izvestiya Physics of the Solid Earth》2010,46(7):613-623
The data on geomagnetic reversals are compared with the changes in the organic world and with the lower-mantle plumes. The
times of the formation of plumes and the times of their appearance on the Earth’s surface relate to the intervals characterized
by the different frequencies of geomagnetic reversals, i.e., there is no interrelation between the formation of plumes and
the frequency of the changes in the geomagnetic field polarity. At the same time, a certain synchronism is observed between
the frequency of the geomagnetic reversals and the boundaries of the biostratigraphic ages, i.e., the changes in the organic
world in the long-period range. A hypothesis is proposed, which explains the change in the sign of the geomagnetic field by
the combined effect of the irregular rotation of the internal core relative to the mantle and the changes in the slope angle
of the axis of the Earth’s rotation, which, in turn, results in synchronous events on the Earth’s surface: the rates of changes
in the organic world. 相似文献
2.
The specific features of the spatial structure and time dynamics of the main geomagnetic field during the 20th century, proceeding
from the present-day concepts of geomagnetic jerks have been studied. The variations, caused by global dissipation of the
geomagnetic field dipole part, have been separated from the regional variations, described by nondipole spatial harmonics
of the spherical harmonic expansion series. It has been indicated that the geomagnetic field westward drift manifests itself
in a limited region of the Earth’s surface, forming the known Brazil anomaly. However, the drift component in the variations
in the geomagnetic field morphological structures is globally found out during the considered almost 100-year period along
the narrow belt around the geomagnetic axis. However, this drift is northwestward in the Northern Hemisphere, and the structures
drift southeastward in the Southern Hemisphere. The detected variations of the drift nature are reflected in the variations
in the integral geomagnetic characteristic, when changes in the position of the Earth’s magnetic center are considered. The
direct correlation between the global geomagnetic variations of the drift nature and the trend variations in the orientation
of the vector of the Earth daily rotation velocity has been detected. 相似文献
3.
D. M. Pechersky 《Izvestiya Physics of the Solid Earth》2007,43(10):844-854
The data on the amplitude of variations in the direction and paleointensity of the geomagnetic field and the frequency of reversals throughout the last 50 Myr near the Paleozoic/Mesozoic and Mesozoic/Cenozoic boundaries, characterized by peaks of magmatic activity of Siberian and Deccan traps, and data on the amplitude of variations in the geomagnetic field direction relative to contemporary world magnetic anomalies are generalized. The boundaries of geological eras are not fixed in recorded paleointensity, polarity, reversal frequency, and variations in the geomagnetic field direction. Against the background of the “normal” field, nearly the same tendency of an increase in the amplitude of field direction variations is observed toward epicenters of contemporary lower mantle plumes; Greenland, Deccan, and Siberian superplumes; and world magnetic anomalies. This suggests a common origin of lower mantle plumes of various formation times, world magnetic anomalies, and the rise in the amplitude of geomagnetic field variations; i.e., all these phenomena are due to a local excitation in the upper part of the liquid core. Large plumes arise in intervals of the most significant changes in the paleointensity (drops or rises), while no correlation exists between the plume generation and the reversal frequency: times of plume formation correlate with the very diverse patterns of the frequency of reversals, from their total absence to maximum frequencies, implying that world magnetic anomalies, variations in the magnetic field direction and paleointensity, and plumes, on the one hand, and field reversals, on the other, have different sources. The time interval between magmatic activity of a plume at the Earth’s surface and its origination at the core-mantle boundary (the time of the plume rise toward the surface) amounts to 20–50 Myr in all cases considered. Different rise times are apparently associated with different paths of the plume rise, “delays” in the plume upward movement, and so on. The spread in “delay” times of each plume can be attributed to uncertainties in age determinations of paleomagnetic study objects and/or the natural remanent magnetization, but it is more probable that this is a result of the formation of a series of plumes (superplumes) in approximately the same region at the core-mantle boundary in the aforementioned time interval. Such an interpretation is supported by the existence of compact clusters of higher field direction amplitudes between 300 and 200 Ma that are possible regions of formation of world magnetic anomalies and plumes. 相似文献
4.
Based on the time series of observational variations of the length of day (LOD) and seismic data in the world, the relations
of the decadal fluctuation and seasonal variation in the Earth’s rotation with global seismic activity are studied in this
paper. The results suggest that there are overall correlations on temporal scale and regional discrepancy on spatial scale
between global seismic activity and the Earth’s variable rotation, especially the seismic activity in the Eurasian seismic
zone (not including southeast Asia) and the Lower California-Eastern Alaska seismic zone correlating well with the Earth’s
variable rotation. According to the relations mentioned above, the observational data of the Earth’s rotation might provide
a referential basis for monitoring global seismic activity.
This project is sponsored by the National Key Basic Research Project and the National Natural Science Foundation of China.
The English version is improved by Prof. Xin-Ling QIN, Institute of Geophysics, SSB, China. 相似文献
5.
M. Yu. Reshetnyak 《Izvestiya Physics of the Solid Earth》2012,48(4):326-334
The eigenvalue problem for Parker’s dynamo model is considered. We study how the intensity of convection in the liquid core
of the Earth affects the generation of the geomagnetic field with different directions of latitudinal field propagation. The
scenarios of transition of the geomagnetic field from frequent to rare reversals are suggested. 相似文献
6.
S. V. Starchenko 《Geomagnetism and Aeronomy》2011,51(3):409-414
The large-scale harmonic magnetic-convective sources of the main geomagnetic field in the Earth’s core have been determined
for the first time. The determination is based on a complete system of eigenfunctions of the magnetic diffusion equation in
a homogeneously conducting sphere, which is surrounded by an insulator. The sources of the main geomagnetic field observed,
which is responsible for the distribution of the electric currents generating this field in the core, are expressed in terms
of large-scale eigenfunctions. In this case, the dipole sources are directly related to the observed geomagnetic dipole, whereas
the quadrupole sources are related to the quadrupole, etc. The time variations in the obtained sources are responsible for
individual spatiotemporal features in the generation or suppression of each Gaussian component of the observed geomagnetic
field. When the commonly accepted observational international geomagnetic reference field (IGRF) models were used to partially
reveal these time variations, it became possible to specify the estimate of the Earth’s core conductivity and determine the
minimum period that can separate us from the commencement of further inversion or excursion. 相似文献
7.
Measurements of solar cosmic ray (SCR) protons in the magnetosphere can be used to verify models of the Earth’s magnetic field.
The latitudinal profiles of precipitating SCRs with energies of 1–90 MeV were measured on the CORONAS-F low-orbiting satellite
during a strong magnetic storm on October 29–30, 2003. A flux of precipitating protons can remain equal to the interplanetary
flux only due to a strong pitch angle diffusion that originates when the radius of the field line curvature is close to that
of the particle rotation Larmor radius. The observed boundaries of the strong diffusion region can be compared with the boundaries
anticipated according to the models of the magnetic field of the Earth’s magnetosphere. The adiabaticity parameter values,
calculated for several instants of the CORONAS-F satellite pass based on the TS05 and parabolic models, do not always correspond
to measurements. How possible changes in the model configurations of the magnetic field can allow us to eliminate discrepancies
with the experiment and to explain why solar protons with energies of several megaelectronvolts penetrate deep in the Earth’s
inner magnetosphere is considered here. 相似文献
8.
Geomagnetism and Aeronomy - A geomagnetic storm is a major disturbance in the Earth’s magnetosphere due to the solar wind entering the magnetosphere and ionosphere, lasting about 1–3... 相似文献
9.
A mathematical modeling method and the global numerical model of the Earth’s upper atmosphere were used to study nighttime enhanced electron density regions (EEDRs) in the ionospheric F2 layer and their possible manifestations at altitudes of the Earth’s plasmasphere. It has been established that EEDRs are formed owing to latitudinally nonuniform longitudinal (along the magnetic field) plasma flows from the plasmasphere into the nighttime ionosphere and the wind transport of ions along geomagnetic field lines. The specific features of the effect of ionospheric-plasmaspheric plasma transport processes, related to their three-dimensional character, on EEDRs have been revealed. 相似文献
10.
The possibility that conditions on the Sun and in the Earth’s magnetosphere can affect human health at the Earth’s surface has been debated for many decades. This work reviews the research undertaken in the field of heliobiology, focusing on the effect of variations of geomagnetic activity on human cardiovascular health. Data from previous research are analysed for their statistical significance, resulting in support for some studies and the undermining of others. Three conclusions are that geomagnetic effects are more pronounced at higher magnetic latitudes, that extremely high as well as extremely low values of geomagnetic activity seem to have adverse health effects and that a subset of the population (10–15%) is predisposed to adverse health due to geomagnetic variations. The reported health effects of anthropogenic sources of electric and magnetic fields are also briefly discussed, as research performed in this area could help to explain the results from studies into natural electric and magnetic field interactions with the human body.Possible mechanisms by which variations in solar and geophysical parameters could affect human health are discussed and the most likely candidates investigated further. Direct effects of natural ELF electric and magnetic fields appear implausible; a mechanism involving some form of resonant absorption is more likely. The idea that the Schumann resonance signals could be the global environmental signal absorbed by the human body, thereby linking geomagnetic activity and human health is investigated. Suppression of melatonin secreted by the pineal gland, possibly via desynchronised biological rhythms, appears to be a promising contender linking geomagnetic activity and human health. There are indications that calcium ions in cells could play a role in one or more mechanisms. It is found to be unlikely that a single mechanism can explain all of the reported phenomena. 相似文献
11.
A. A. Karakhanyan G. A. Zherebtsov V. A. Kovalenko S. I. Molodykh 《Geomagnetism and Aeronomy》2011,51(8):1155-1159
The Earth’s crossings of the magnetic sector boundaries are accompanied by changes in the magnetosphere, ionosphere, and troposphere.
We considered the baric field’s response to the crossing of the inter-planetary magnetic field (IMF) sector boundaries during
a geomagnetically quiet period. The IMF sign is shown to affect atmospheric pressure in high-latitude regions. The efficiency
and sign of the relationship vary during the year. The baric field response to the Earth’s crossing of the IMF sector boundaries
is most distinct during equinoxes. It is shown that, during a geomagnetically quiet period, the circulation processes in the
atmosphere drive the changes in the atmospheric pressure when the Earth passes from one IMF sector into another. 相似文献
12.
Besides generating seismic waves, which eventually dissipate, an earthquake also generates a static displacement field everywhere within the Earth. This global displacement field rearranges the Earth’s mass thereby causing the Earth’s rotation and gravitational field to change. The size of this change depends upon the magnitude, focal mechanism, and location of the earthquake. The Sumatran earthquake of December 26, 2004 is the largest earthquake to have occurred since the 1960 Chilean earthquake. Using a spherical, layered Earth model, the coseismic effect of the Sumatran earthquake upon the Earth’s length-of-day, polar motion, and low-degree harmonic coefficients of the gravitational field are computed. Using a model of the earthquake source that is composed of five subevents having a total moment-magnitude M
w
of 9.3, it is found that this earthquake should have caused the length-of-day to decrease by 6.8 microseconds, the position of the Earth’s generalized figure axis to shift 2.32 milliarcseconds towards 127° E longitude, the Earth’s oblateness J
2 to decrease by 2.37 × 10−11 and the Earth’s pear-shapedness J
3 to decrease by 0.63 × 10−11. The predicted change in the length-of-day, position of the generalized figure axis, and J
3 are probably not detectable by current measurement systems. But the predicted change in oblateness is perhaps detectable if other effects, such as those of the atmosphere, oceans, and continental water storage, can be adequately removed from the observations. 相似文献
13.
The effect of the mutual orientation of the Poynting vector P of the electromagnetic energy density in the solar wind and the vector M of the Earth’s magnetic moment (taking into account its orbital and diurnal motions) on the geomagnetic activity has been
examined for the first time using the measurements of the solar wind parameters on the Earth orbit in 1963–2005. The component
P
m of the vector P along the vector M is shown to have a pronounced annual variation with the extrema in November and May and a diurnal variation with the extrema
at ∼6 and 18 UT. The phases of the variations are shown to be determined only by the geometric parameters and are independent
of the sign of the sector structure of the interplanetary magnetic field. The experimental data on the planetary and high-latitude
geomagnetic activity, which is a response to changes in the orientation of P relative to M, are presented. The power of the sources of the electromagnetic energy of the solar wind during strong geomagnetic disturbances
is also estimated. 相似文献
14.
Disturbances produced by geomagnetic storms in the higher regions of the Earth’s atmosphere, such as in the ionospheric F2
region and in the lower ionosphere, are relatively better known than those produced at lower altitudes, where the effects
of geomagnetic storms have been little studied. During magnetically perturbed conditions, some changes in pressure and temperature
at high latitudes have been observed, from the surface level to heights of around 30 km, but there are no morphological studies
and/or patterns of behavior. Moreover, the physical mechanisms are still unknown and what exists is a matter of controversy.
Thus, the aim of this paper is to contribute to the vertical profile of the effects of geomagnetic storms as observed in the
lower sectors of the atmosphere. For that, we study the variations of two atmospheric parameters (temperature and wind speed)
during an intense geomagnetic storm (minimum Dst = −300 nT), at heights between about 6 km and 20 km. The data used were obtained
from weather balloon flights carried out at low, mid and mid-high latitudes in different longitudinal sectors of the northern
hemisphere, which took place twice per day: 00:00 and 12:00 UT. Small, but statistically significant changes in temperature
and in zonal component of the neutral winds are observed at mid-high latitudes, which can be linked to short-term geomagnetic
forcing. However, the results show different atmospheric response to the geomagnetic storm in the different longitudinal sectors
at tropospheric and stratospheric levels, which suggests a regional character of the geomagnetic storms effects at tropospheric
levels. 相似文献
15.
The structure and physical conditions in 104 coronal mass ejections (CMEs) with a clear-cut leading shock front have been
considered using satellite data for 1996–2008. In 99% of cases, the action of increased shock front dynamic pressure on the
Earth’s magnetosphere resulted in the origination of geomagnetic storms with sudden commencement. 相似文献
16.
O. V. Kozyreva I. N. Myagkova E. E. Antonova N. G. Kleimenova 《Geomagnetism and Aeronomy》2009,49(6):741-749
Precipitation of electrons with energies of 0.3–1.5 MeV has been analyzed based on the CORONAL-F satellite data at polar latitudes
of the Northern Hemisphere on December 13, 2003. The instants of electron precipitation have been compared with the ground-based
observations of geomagnetic disturbances and auroras near the satellite orbit projection. It has been indicated that precipitation
of energetic electrons in the high-latitude nightside sector is accompanied by the simultaneous development of bay-like magnetic
field disturbances on the Earth’s surface and the appearance of riometer absorption bursts and Pi3 geomagnetic pulsations,
and auroras. 相似文献
17.
Based on the WIND and GOES satellite data on the solar wind and IMF parameters and the data on the surface magnetic field,
it has been indicated that the secondary MHD rarefaction wave can affect the geomagnetic field during a storm sudden commencement
(SSC) event. The secondary rarefaction wave originates in the magnetosheath when the shock wave interacts with the Earth’s
magnetosphere. 相似文献
18.
19.
The elasto-gravitational deformation response of the Earth’s solid parts to the perturbations of the pressure and gravity
on the core-mantle boundary (CMB) and the solid inner core boundary (ICB), due to the dynamical behaviors of the fluid outer
core (FOC), is discussed. The internal load Love numbers, which are formulized in a general form in this study, are employed
to describe the Earth’s deformation. The preliminary reference Earth model (PREM) is used as an example to calculate the internal
load Love numbers on the Earth’s surface, CMB and ICB, respectively. The characteristics of the Earth’s deformation variation
with the depth and the perturbation periods on the boundaries of the FOC are also investigated. The numerical results indicate
that the internal load Love numbers decrease quickly with the increasing degree of the spherical harmonics of the displacement
and depend strongly on the perturbation frequencies, especially on the high frequencies. The results, obtained in this work,
can be used to construct the boundary conditions for the core dynamics of the long-period oscillations of the Earth’s fluid
outer core.
Foundation item: State Natural Science Foundation of China (40174022 and 49925411) and the Projects from Chinese Academy of Sciences (KZCX2-106
and KZ952-J1-411). 相似文献
20.
Mabel Mena Avto Goguitchaichvili Miguel Cervantes Solano Juan Francisco Vilas 《Studia Geophysica et Geodaetica》2011,55(2):279-309
The Early Cretaceous may be considered a key period for understanding the evolution of the Earth’s magnetic field. Some still
unsolved problems are related to the mode of paleosecular variation (PSV) of the Earth’s magnetic field before and during
the Cretaceous Normal Superchron. We report here a detailed rock-magnetic, paleomagnetic and paleointensity investigation
from 28 lava flows (331 standard paleomagnetic cores) collected in the Argentinean part of the Parana Flood Basalts (Formation
Posadas) in order to contribute to the study of PSV during the early Cretaceous and to obtain precise Cretaceous paleomagnetic
pole positions for stable South America. The average paleofield direction is precisely determined from 26 sites, which show
small within-site dispersion and high directional stability. Five sites show evidences for the self-reversal of thermoremanent
magnetization. 23 sites yielded normal polarity magnetization and only 3 are reversely magnetized. Moving windows averages
were used to analyze the sequential variation of virtual geomagnetic pole’s (VGP) axial positions. Interestingly, the axial
average VGP path traces an almost complete cycle around the geographical pole and passes near the location of all previously
published Paraná Magmatic Province poles. Both paleomagnetic poles and average VGP paths are significantly different from
the pole position suggested by fixed hotspot reconstructions, which may be due to true polar wander or the hotspot motion
itself. Only 15 samples from 5 individual basaltic lava flows, yielded acceptable paleointensity estimates. The site mean
paleointensities range from 25.2 ± 2.2 to 44.0 ± 2.2 μT. The virtual dipole moments (VDMs) range from 4.8 to 9.9 × 1022 Am2. This correspond to a mean value of 7.7 ± 2.1 × 1022 Am2 which is 96% of the present day geomagnetic field strength. These intensities agree with the relatively high values already
reported for Early Cretaceous, which are consistent with some inferences from computer simulations previously published. 相似文献